Seleção de isolados rizobianos de mucuna preta (Stizolobium aterrimum Piper e Tracy)

Abstract

The panorama of rapid population growth alert to the challenge of global food security demanding increased food production. Green manuring with legumes such as velvet bean, proves important in the growth of mainly N, in the system, due to the biological N2 fixation (BNF), reducing the use of mineral fertilizers, directly linked to agricultural production. The BNF can be maximized by inoculation with efficient and competitive strains. Therefore, the objective was to select isolates rizobianos nodules of velvet bean, efficient and competitive in home condition of vegetation and then experimental field. The experiment in greenhouse was composed of 39 isolated rizobianos, four doses of nitrogen fertilizer (N) in the form of urea (60, 120, 180 and 240 kg ha-1), one without inoculation and without N treatment and another with inoculating the mixture of strains recommended SEMIA6156-6158 in a completely randomized design with five repetitions. Cultivation was carried out in plastic bags of polyethylene filled with 2.5 kg of non-sterile soil for 45 days. While the field experiment consisted of five isolates selected in a greenhouse, one dose of N in the form of urea (80 kg ha-1), one treatment without inoculation and without N, and inoculation of the mixture of strains recommended in dryland system in a randomized block design with four replications for 45 days. The collection of soil and field tests were conducted in Experimental Cane Sugar Carpina Station belonging to the Federal Rural University of Pernambuco (UFRPE), located in the city of Carpina, Pernambuco state. The greenhouse experiment was conducted at UFRPE in the city of Recife, Pernambuco state. In both experiments the soil was fixed with dolomitic limestone at a dose of 0.60 t ha-1 and 0.65 t ha-1, respectively. The basic fertilization in both experiments was performed with superphosphate (60 kg P ha-1) and potassium chloride (40 kg K ha-1). The preparation of the inoculant started the cultivation of bacteria in YM medium (120 rpm, 28 ° C) for 72 hours. The following variables were measured: dry mass of nodules (MSN), the aerial part (MSPA) and root (MSR). Determined the total nitrogen concentration in the shoot tissues (CNPA) and the accumulation of N in the shoot (ANPA). Also, assessment of the relative efficiency compared with 120 kg N ha-1 and calculated N Dose, for the greenhouse experiment, and 80 kg N ha-1 for the field experiment. We also assessed the Pearson correlation between variables. It was performed by analysis of variance (ANOVA) and multiple comparison test medium by Scott-Knott test (p ≤ 0.05). The T2.19A and T1.17M isolates present great potential for the production of inoculants because they promote nitrogen accumulation in the shoot, in the field, significantly higher than the application of 80 kg N ha-1, to inoculation with the mixture of strains recommended SEMIA6156-6158 and treatment without inoculation and without N. The MSPA was influenced by N levels.